GB/T 42660-2023Aerosol particle number concentration - Calibration of condensation particle counters (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents" Drafting.

This document is equivalent to ISO 27891:2015 "Calibration of aerosol particle number concentration condensation particle counters".

This document has made the following minimal editorial changes.

---Replace "ISO/IEC 17025" with "GB/T 27025 or ISO/IEC 17025".

Please note that some content in this document may be subject to patents. The publisher of this document assumes no responsibility for identifying patents.

Introduction

A condensation particle counter (CPC) is a device that measures the number concentration of tiny aerosol particles. Generality of all different types of CPC the principle is. ultrafine and nanoparticles condense and grow through supersaturated vapor to form droplets that can be detected by optical methods. The droplets pass through the detection method.

When measuring the area, it is illuminated by a focused beam and detected with a photodetector, and finally the droplets are counted using the light scattering method. These counts combined from a known volume of sample gas, the particle number concentration can be obtained. At low concentrations, CPC can detect individual particles and obtain the absolute number of particles.

concentration.

CPCs on the market use different working fluids to generate vapor, such as n-butanol, isopropyl alcohol or water. In addition, different principles are used in applications to achieve the required supersaturation of the sample gas. The most common CPC uses the principle of laminar flow diffusion heat transfer. The diffusion constant of the working fluid determines the required Whether to heat or cool to start condensation is also the design principle of laminar flow CPC. Turbulent flow CPC is less common, and its working fluid and clean the air first reaches saturation, and then turbulently mixes with the sample gas to reach supersaturation. Figure 1 shows one of the most common implementations by heating the saturator and condenser Schematic diagram of laminar flow CPC type.

Indexing serial number description.

1---Aerosol inlet; 4---Nanoparticles; 7---Liquid droplets; 10---Optical receiver;

2---working fluid reservoir; 5---thermoelectric cooling and heating device; 8---light source; 11---photoelectric detector;

3---Heating saturation chamber; 6---Condensation chamber; 9---Optical illuminator; 12---Aerosol outlet.

Figure 1 Principle of laminar flow CPC

The measurement accuracy of CPC depends on several influences. For example, an error in flow rate will cause an error in concentration. Other possible error sources include these include. overlay errors at very high concentrations, insufficient activation of very small particles, and loss of particles from the inlet to the detection area. Refined for accurate measurement, the CPC needs to be calibrated.

"Calibration" of CPC typically uses a Faraday Cup Aerosol Electrometer (FCAE) as a reference tool [33][36]. in many cases Below, the purpose of "calibration" is to determine the detection limit for small size particles. Because the detection efficiency of FCAE is considered to be the best for particles of any size Consistent, therefore FCAE is often used as a reference method. The same number and concentration of singly charged aerosol particles of different sizes are provided to when CPC and FCAE are used, the concentration ratio of the calibrated CPC to FCAE is the detection efficiency of the CPC.

This document proposes two different CPC calibration methods. one is the same as the traditional method mentioned above, calibrating the CPC by FCAE, and the FCAE must have an authoritative calibration certificate including particle number concentration, particle size and composition before it can be used. The other is to use reference CPC Calibration CPC, reference CPC also has authoritative calibration certificates including particle number concentration, particle size and composition. The above two calibrations the authoritative calibration certificate in the method refers to the one issued by a laboratory accredited by GB/T 27025 or ISO/IEC 17025 or equivalent standards.

Calibration certificate, the calibration type and scope of which are within the scope of laboratory accreditation, or issued by a designated agency or national metrology institute that can provide relevant calibration services Calibration certificate issued by the organization, its measurement method meets the requirements of GB/T 27025 or ISO/IEC 17025.

There are two main known sources of error in CPC calibration. one is due to the presence of multiply charged particles, and the other is caused by calibrating the CPC input.

There is a number concentration deviation between the inlet of the instrument and the inlet of the reference instrument. Evaluation and correction of these factors are included in the calibration procedure. These methods this is explained in detail in this document.

This document is intended for.

---CPC users with internal calibration procedures (such as for environmental or vehicle emission purposes);

---CPC manufacturers that certify and recertify the performance of their instruments;

---Technical laboratories that provide CPC calibration services, including national metrology agencies that are establishing support for quantity concentration measurement equipment.

Aerosol particle number concentration Calibration of Condensation Nucleus Particle Counter

1 Scope

This document describes the detection efficiency of a calibrated condensation particle counter (CPC) when the particle number concentration range is 1cm-3 to 105cm-3.

Methods and their associated measurement uncertainties. Typically, detection efficiency will depend on particle number concentration, particle size, and composition. described in this document the particle size range covered by the calibration method is approximately 5nm~1000nm.

These methods can be used to determine the CPC calibration factor when the detection efficiency is relatively constant (stable efficiency) in the larger particle size range, and when the detection efficiency is relatively constant (stable efficiency) in the smaller particle size range, can be used to characterize the lower limit of CPC detection efficiency when approaching a lower detection limit. See Appendix A for more detailed parameters.

This document is suitable for the calibration of CPCs with air inlet flow rates between 0.1L/min and 5L/min.

This document describes a method for estimating the uncertainty in the CPC calibration process.

2 Normative reference documents

The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, the dated quotations for undated referenced documents, only the version corresponding to that date applies to this document; for undated referenced documents, the latest version (including all amendments) applies to this document.

3 Terms and definitions

The following terms and definitions apply to this document.

aerosol

A relatively stable suspension system of liquid and/or solid particles in the atmosphere.

Bipolar charging device bipolarcharger the aerosol particles pass through the positive and negative charge areas in the device, so that the aerosol particles reach charge balance and the charge distribution is particle size-related.

Particle charge regulator.

NOTE. Exposing aerosol particles to an electrically neutral gas composed of positive and negative charges at a sufficiently high charge density and for a sufficiently long time Within, the net charge of the aerosol is almost zero, thus reaching equilibrium (also called charge neutralization).

Calibration

A set of operations under specific conditions. The first step is to establish the quantity value (uncertainty) provided by the measurement standard and the corresponding indication value (uncertainty) of the instrument to be calibrated.

certainty); the second step is to use this information to establish the relationship between the indication and the measurement result.

Note 1.Calibration can be expressed in the form of text descriptions, calibration functions, calibration diagrams, calibration curves or calibration tables. In some cases, this may include measuring Additive or multiplier correction of indications and uncertainties.

Note 2.Calibration should not be confused with the adjustment of the measurement system, often mistakenly called "self-calibration", nor should it be confused with the verification of calibration.